What Treatment Should Be Given To One Suffering With Parkinson's Disease For Stiffness In Joints And Muscles, Swallowing Difficulty ?

I want to discuss about my grand father Age 85: Suffering from Parkinson disease for the last 20 years his joint and muscles have become rigid.he is completely on bed.pampers are applied to him. till 4-5 days before he was ale to sit and talk but now he can hardly talk and also feeling difficulty in swallowing .we are giving him liquid food but with great difficulty.we can hardly understand what he wants to say.he was also heart patient suffering from angina and took medicines for this for a long time but now he is not taking these medicines. dementia has also developed.doctor has prescribed medicines sinemet tab and requip but of no benefit.for sleep disturbance revotril is being given to him.we want your advice and suggestion so that he may take food easily and muscles rigidity is controlled and others.here the doctor has told us that it is an old age related disease,nothing can be done,carry on nursing only.kindly guide us in detail and prescribe medicines.